The register adults use when talking to each other is more complex in nature if compared to the one they use when talking to the child (Child Directed Speech, CDS). For evidencing such hypothesis, we analyzed adults’ utterances with embedded clauses introduced by subordinate adverbial conjunctions when they spoke to each other and to the child and by the way how they used them; Data were taken from PAU003’s file, recorded during Scliar-Cabral’s doctoral thesis and available at http://childes.psy.cmu.edu/data/Romance/ Portuguese/florianopolis.zip. MacWhinney (1995), Brown (1973), and Scliar-Cabral (1977) categories were used for analysing the data. For the Childes Platform, they were digitized by CNPq Scientific Initiation grantees, under Scliar-Cabral’s guidance and the grantee Íris Marjorie BÖING IMHOF (2014) participated specifically in the research being described.The child, even when exposed to certain syntactic and lexical complexity (input) utterances, only takes from them, what his linguistic and cognitive maturity allows (intake). Although exposed to subordinate adverbial conjunctions six types, the child only reproduced one conjunction type, the causal “because” (Port. ‘porque’), even though the temporal conjunction “when” (Port. ‘quando’) showed the highest frequency in adults’ Child Directed Speech. It can be inferred, then, that the conjunction “because” presents less processing complexity. The other studied hypothesis is that the child did not issue any temporal conjunction, because it statements addressed by adults to him were very extensive and, therefore, more difficult to process.
In addition, when adults talked to each other, they produced thirteen types of subordinate conjunctions, with the causal conjunction “because” being more frequent, followed by the temporal conjunction “when”. This survey evidences that the subordinate adverbial conjunctions are items of late acquisition, which depend on the child’s cognitive and linguistic development, input and processing. Therefore, the Child Directed Speech items frequency, their syntactic complexity and communicative functions interfere in the child language acquisition.